Reinforcement of the third buttressing point lateral cortex

5.4.1 Stability problems at the third buttressing point - varus and rotational movements as well as loss of reduction

In Sect. 4.2.1, we mentioned that we had designed a prominent 2 mm two-hole plate for the fixation of the caudal Smith-Petersen nail. During the preparation of nailing the lateral cortex often bursts during chiseling and the stabilizing action of the third buttressing point is lost. The plate could not prevent movements and backing-out of the nail from the femoral head. A loss of reduction with tilting in varus ensued. The "distant" buttressing of the sliding screw had only a tension band effect. Protection against rotation was assured by the flanges of the nail.

Our Swedish colleagues did not use a lateral anchorage of the cannulated screws whereas our goal had been from the beginning to obtain such an anchorage (see Sect. 4.2.4). In some of the early cases we used a modified 1/3 tubular plate but abandoned this method soon due to technical difficulties (tension at the screw ends, need for larger exposure). Therefore we designed a 2 mm two-hole plate having a tension band effect and the relevant in struments for percutaneous insertion. To reduce further the risk of displacement in rotation and to ascertain the desired sliding of screws we flattened the end of the screw and the corresponding hole in the plate. While analyzing in the meantime the results of fractures fixed with two screws without a tension plate we noticed these details that confirmed our ideas (Fekete et al, 1992).

To assess the stability of internal fixation we compared the postoperative radiographs with those done at follow-up. We had to realize that in 29 out of 134 patients in whom the fractures were treated without a lateral plate, a slight change in the position of the screws against each other had occurred. The initial parallel position had been lost. We concluded that a slight displacement in varus and rotation of the fracture had taken place. After introduction of the 2 mm two-hole plate the incidence of rotational movements decreased markedly: among the 29 first patients treated with this plate, a rotational displacement was observed only twice.

An additional indication of overloading of the third buttressing point in instances where no plate was used was reflected by the fact, that in some patients the lateral cortex surrounding the caudal screw thickened some months after internal fixation.

Internal Fixation
b

Fig. 149. Thickening of the lateral cortex around the screw end (see Fig. 93). A magnification of part of the a.-p. radiograph illustrates the difference in thickness of the lateral cortex; a. Postoperative radiograph; b. Radiograph taken after nine months: the increase in thickness is well seen. It seems that not only the closeness of the screws but also the absence of a plate led to an irritation of the overloaded lateral cortex

5.4.2 Thickening of the lateral cortex after screw fixation without a 2 mm two-hole plate

Several of the 134 above mentioned patients complained about pain after three to six months lasting a few weeks. Under weight bearing this pain increased in the beginning and then decreased. Initially we failed to find an explanation. Reexamina-tion of late follow-up radiographs revealed a marked thickening (doubling) of the lateral cortex involving an area of 2 to 3 cm around the end of the caudal screw in 12 patients (Fig. 149).

We interpreted this phenomenon as being caused by load-induced small screw movements that induce an osteogenesis followed by the formation of an irritation callus and then a supporting periosteal callus. Pain is felt until this "biologic plate" solidly supports the screw (Fig. 150).

These examples show that the lateral cortex cannot always respond to the demands put on the third buttressing point. Even in perfectly

Fig. 150. Thickening of the lateral cortex in another patient.

66-year-old patient; a. She fell at home and suffered a left Garden-III multifragmental fracture; b, c. Internal fixation with two cannula-ted screws was done inside six hours. During the subsequent weeks the patient complained at times about hip pain that increased with weight bearing. Six weeks later bone resorption around the caudal screw was noted; d. This osteolysis became more marked after 10 weeks. After six months the pain subsided, the thickening of the lateral cortex is evident; e. During a follow-up after one year no progression was seen b a c d e

Fig. 150. Thickening of the lateral cortex in another patient.

66-year-old patient; a. She fell at home and suffered a left Garden-III multifragmental fracture; b, c. Internal fixation with two cannula-ted screws was done inside six hours. During the subsequent weeks the patient complained at times about hip pain that increased with weight bearing. Six weeks later bone resorption around the caudal screw was noted; d. This osteolysis became more marked after 10 weeks. After six months the pain subsided, the thickening of the lateral cortex is evident; e. During a follow-up after one year no progression was seen stabilized fractures micromovements occur, these may increase in the presence of less stable fixation without a plate (errors in internal fixation, multi-fragmentary and comminuted fractures). Other factors such as osteoporosis, age, weight bearing and body weight will determine, whether the fracture will consolidate (possibly with a "biologic plate") or whether a loss of reduction will take place. To avoid the latter complication it is mandatory to reinforce the lateral cortex, particularly in the presence of osteoporosis in older patients. If the caudal screw finds support on Adam's arch and thus a two-arm leverage is operative, a 2 mm two-hole plate exerting a tension band effect is sufficient in the majority of patients. The use of a heavier and bigger plate is not warranted.

Fig. 151. Photograph of the experimental set-up.

5.4.3 Investigations testing the effectiveness of a 2 mm two-hole plate

We believed that an experimental investigation of the action of the 2 mm two-hole plate was warranted. These tests were executed at the Department of Material Science and Mechanical Technology of the Budapest University of Technology and Economics (BUTE) in 1992.

A Pauwels-II fracture was produced in paired proximal femoral specimens of human cadavers by osteotomizing the neck at 45°. The osteotomy was then properly stabilized with two cannulated screws. To compare the effectiveness of a 2 mm two-hole plate, it was used on one side and omitted on the other. The diaphyseal stump was secured in an appropriate holding device of a TIRA test 2300 apparatus and a linearly increasing force applied to the weight bearing surface of the femoral head in a direction parallel to the longitudinal axis of the femur (Fig. 151).

Comparative measurements were executed on four pairs of specimens. The force applied was continuously graphically registered until a displacement of the femoral head occurred. The load to cause a displacement of fractures secured with a 2 mm two-hole plate was one and a half times greater (Fig. 152).

These tests proved that the 2 mm two-hole plate increased the stability of the lateral cortex by approximately 50%. In other words, this plate is sufficient to increase the stability when the Adam's arch is intact.

Fig. 151. Photograph of the experimental set-up.

Fig. 152. Experimental comparison of the stability of fixation of femoral neck fractures with only two screws and supplementation with a 2 mm plate.

The pairs of proximal femora are identified by Roman numbers and different shades. It is evident that the force (Fmax in N) to obtain a displacement of the femoral head is 50% greater when a 2 mm two-hole plate was used two screws two screws + 2 mm two hole plate two screws two screws + 2 mm two hole plate

Fig. 152. Experimental comparison of the stability of fixation of femoral neck fractures with only two screws and supplementation with a 2 mm plate.

The pairs of proximal femora are identified by Roman numbers and different shades. It is evident that the force (Fmax in N) to obtain a displacement of the femoral head is 50% greater when a 2 mm two-hole plate was used

5.4.4 Proper attachment of the 2 mm two-hole plate

As already stated the goal of internal fixation with sliding screws combined with a plate exerting a tension band effect has been the protection against rotation. The use of a conventional cerclage did not fulfill this requirement. Also the percutaneous placement over the screw ends would have been technically most difficult. For this reason the need arose for further development of the 2 mm plate.

The end of the screw was flattened over a distance of 30 mm and the corresponding hole in the plate squared on two sides only. A flattening extending over the entire screw length was purposely omitted given the risk of screw bending at the level at the second buttressing point, the Adam's arch. An even better protection against rotation would have been a squaring of the screw's end and to make square holes in the plate. The disadvantage, however, would have been the absence of a cranial and caudal contact of the screw shank in the round drill hole in the lateral cortex (Fig. 153).

To compensate for any weakening caused by the bilateral flattening the diameter of the screw's shank was increased by 1 mm. The identical design of screw end and plate hole geometry allowed a sliding of the screw.

The angle of the plate is 140°. Its thin design, however, allows adaptation to a certain degree of the screw to the neck-shaft angle. If in the presence of an extreme coxa valga a steeper angle of screw insertion is necessary, the angle of the plate can be changed with a pair of flat-nosed pliers. A deeper insertion of the screw end may become necessary in very slim patients.

It is important to attach the 2 mm plate to the screw end without any tension. A freehand percutaneous insertion of the 2 mm plate can be problematic in moderately heavy patients. Manipulations in a small wound may cause a major soft tissue trauma. In addition, it may be difficult to hold the plate with the hand during drilling, tapping and insertion of the 4.5 mm cortical screw while avoiding any tension. Therefore, the use of a seating instrument for proper placement of the plate is recommended. It permits to hold the plate in proper position during radio-

graphic control in both planes and to protect the soft tissue as well.

When using several modifications such as three-hole plate stabilization of two screws or double DCD plate, care has to be taken to orient the flattened screw end parallel to each other and to the femoral diaphysis. In the absence of such a precaution the plate cannot be placed properly or only with the use

Fig. 153. Ideal position of the distal screw ends in the lateral cortex

During screw insertion care has to be taken to place the squared surfaces parallel to the femoral diaphysis. In this way the rounded screw shank surfaces will be in perfect contact with the cranial and caudal borders of the drill hole in the cortex

Fig. 153. Ideal position of the distal screw ends in the lateral cortex

During screw insertion care has to be taken to place the squared surfaces parallel to the femoral diaphysis. In this way the rounded screw shank surfaces will be in perfect contact with the cranial and caudal borders of the drill hole in the cortex

Fig. 154. Ideal position of the distal screw ends in the lateral cortex when using a 2 mm three-hole plate holding two screws or a DCD plate (schema).

The line connecting the end of both screws runs parallel to axis of the femoral diaphysis of great force causing unwarranted tension and possibly leading to deformation and resulting in complications (Fig. 154, see also Sect. 5.7, point 8 and Fig. 167).

5.4.5 Clinical examples of stabilization with a 2 mm two-hole plate

The patient shown in Fig. 94 attracted our attention to the fact that in an initially undisplaced Garden-II fracture after internal fixation with only two screws a displacement can occur after a new fall. In this instance a severe rotational displacement also occurred. For this reason we recommend the use of a 2 mm two-hole plate not only in Garden-III and -IV fractures but also in every Garden-II fracture and in Garden-I fractures when:

- Initially a marked antecurvature or tilting in varus was present and reduced;

- The patient is older than 80 years (osteoporosis);

- A repeated fall can be anticipated (confused patient, alcohol abuse, neurologic diseases such as epilepsy and Parkinson disease) (Fig. 155).

The next example reinforces the importance of a proper placement of the screw ends. The faulty surgical technique contributed also to a deep joint infection (Fig. 156).

Patient Fall During Seizure

Fig. 155. The preventive action of a 2 mm two-hole plate during repeated falls of an epileptic patient.

The 69-year-old woman fell in a nursing home during an epileptic seizure; a, b. She suffered a right medial Garden-IV fracture; c, d. 36 hours later we internally fixed the fracture with two cannulated screws and a 2 mm two-hole plate; e, f. Three months later the patient fell again during a grand mal seizure and suffered a left Garden-I neck fracture; g, h. This fracture was initially treated with two cannulated screws and a plate; i, j. Radiographs of the right hip performed after the second fall show that the right neck fracture that had been internally fixed with screws and a plate did not displace during this fall in spite of the fact that after three months a bony consolidation could not have been expected. The more stable internal fixation prevented a displacement during the epileptic seizure

Fig. 155. The preventive action of a 2 mm two-hole plate during repeated falls of an epileptic patient.

The 69-year-old woman fell in a nursing home during an epileptic seizure; a, b. She suffered a right medial Garden-IV fracture; c, d. 36 hours later we internally fixed the fracture with two cannulated screws and a 2 mm two-hole plate; e, f. Three months later the patient fell again during a grand mal seizure and suffered a left Garden-I neck fracture; g, h. This fracture was initially treated with two cannulated screws and a plate; i, j. Radiographs of the right hip performed after the second fall show that the right neck fracture that had been internally fixed with screws and a plate did not displace during this fall in spite of the fact that after three months a bony consolidation could not have been expected. The more stable internal fixation prevented a displacement during the epileptic seizure

Internal Fixator Image

Fig. 156. Consequences of an incorrect placement of a 2 mm three-hole plate anchoring two screws.

64-year-old woman who underwent an aorto-bifemoral bypass surgery three months earlier. This intervention was followed by a revision surgery for an abscess in the Douglas cul-de-sac. She fell on the day of admission; a, b. We diagnosed a Garden-III-IV fracture with slight varus tilting and marked displacement in antecurvature; c, d. The fracture was treated with two cannulated screws. During surgery the surgeon diagnosed a severe osteoporosis and decided after screw implantation in favor of a plate attached to both screws. A plate bending was necessary and was achieved with great difficulties resulting in a prolonged operating time. Fever developed postoperatively. A wound revision was done on the 11th postoperative day on account of a superficial infection. During debridement it was noted that the plate was under tension and therefore it was removed. Six weeks later subfebrile temperature and parameters of inflammation persisted in spite of antibiotic therapy; e, f. A deep infection with disappearance of the joint space had developed necessitating later a Girdlestone resection. We believe that the cause of this complication has been twofold: due to a persisting remote abdominal septic process and due to the prolonged operating time on account of technical difficulties

Fig. 156. Consequences of an incorrect placement of a 2 mm three-hole plate anchoring two screws.

64-year-old woman who underwent an aorto-bifemoral bypass surgery three months earlier. This intervention was followed by a revision surgery for an abscess in the Douglas cul-de-sac. She fell on the day of admission; a, b. We diagnosed a Garden-III-IV fracture with slight varus tilting and marked displacement in antecurvature; c, d. The fracture was treated with two cannulated screws. During surgery the surgeon diagnosed a severe osteoporosis and decided after screw implantation in favor of a plate attached to both screws. A plate bending was necessary and was achieved with great difficulties resulting in a prolonged operating time. Fever developed postoperatively. A wound revision was done on the 11th postoperative day on account of a superficial infection. During debridement it was noted that the plate was under tension and therefore it was removed. Six weeks later subfebrile temperature and parameters of inflammation persisted in spite of antibiotic therapy; e, f. A deep infection with disappearance of the joint space had developed necessitating later a Girdlestone resection. We believe that the cause of this complication has been twofold: due to a persisting remote abdominal septic process and due to the prolonged operating time on account of technical difficulties

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